During the fabrication process of a wafer, forming metal lines of the integrate circuits on the wafer is an important step in the process. The metal lines may be formed by an electroplating process or a physical vapor deposition (PVD) process. To increase the integration density of a wafer, the useable area of the wafer is expanded to reach the very near edge of the wafer. As a result, metal lines are also formed on the very near edge of the wafer. However, unwanted residual metal on the wafer edge should be removed by a so-called Edge Bevel Removal (EBR) process. Since the edge bevel area is adjacent to the useable area, the EBR process is controlled to ensure that an etchant etches the edge bevel area without harming the useable area. After the EBR process, wafers are monitored to determine if any abnormal wafer edge occurs. Thus, the quality of fabricated wafers is affected by the precision of the monitoring process. Moreover, the monitoring process may also affect the speed of the fabrication process. It may thus be desirable to provide a reliable and accurate monitoring method to increase the yield rate of semiconductor wafers.
Like reference symbols in the various drawings indicate like elements.